Preparation, analysis and toxicity characterisation of the redox metabolites of the azo food dye tartrazine

Tartrazine (E102, FD&C Yellow 5) is a vibrant yellow azo dye added to many processed foods. The safety of this ubiquitous chemical has not been fully elucidated, and it has been linked to allergic reactions and ADHD in some individuals. In our study, bacterial species isolated from human stool d...

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Published in:Food and chemical toxicology 2023-12, Vol.182, p.114193-114193, Article 114193
Main Authors: Pay, Ruth, Sharrock, Abigail V, Elder, Riley, Maré, Alaigne, Bracegirdle, Joe, Torres, Dan, Malone, Niall, Vorster, Jan, Kelly, Libusha, Ryan, Ali, Josephy, P David, Allen-Vercoe, Emma, Ackerley, David F, Keyzers, Robert A, Harvey, Joanne E
Format: Article
Language:English
Subjects:
Azo Compounds - toxicity
Carboxylic Acids
HEK293 Cells
Humans
Oxidation-Reduction
Pyrazoles
Tartrazine - chemistry
Tartrazine - toxicity
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Summary:Tartrazine (E102, FD&C Yellow 5) is a vibrant yellow azo dye added to many processed foods. The safety of this ubiquitous chemical has not been fully elucidated, and it has been linked to allergic reactions and ADHD in some individuals. In our study, bacterial species isolated from human stool decolourised tartrazine and, upon exposure to air, a purple compound formed. Tartrazine is known to undergo reduction in the gut to sulfanilic acid and 4-amino-3-carboxy-5-hydroxy-1-(4-sulfophenyl)pyrazole (SCAP). These metabolites and their derivatives are relevant to the toxicology of tartrazine. The toxicity of sulfanilic acid has been studied before, but the oxidative instability of SCAP has previously prevented full characterisation. We have verified the chemical identity of SCAP and confirmed that the purple-coloured oxidation derivative is 4-(3-carboxy-5-hydroxy-1-(4-sulfophenyl)-1H-pyrazol-4-yl)imino-5-oxo-1-(4-sulfophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic acid (purpurazoic acid, PPA), as proposed by Westöö in 1965. A yellow derivative of SCAP is proposed to be the hydrolysed oxidation product, 4,5-dioxo-1-(4-sulfophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic acid. SCAP and PPA are moderately toxic to human cells (IC 89 and 78 μM against HEK-293, respectively), but had no apparent effect on Escherichia coli and Bacillus subtilis bacteria. These results prompt further analyses of the toxicology of tartrazine and its derivatives.
ISSN:0278-6915
1873-6351
DOI:10.1016/j.fct.2023.114193